O. hygropetricus Kieffer, 1911 = O. fuscimanus (Kieffer in Kieffer and Thienemann, 1908) and O. species B in (Cranston, 1982).
Subgenus Eudactylocladius Thienemann, 1935
Body
Medium sized larvae up to 8 mm long. The L4 setae are simpel and < 110 µm. The anterior and posterior parapods are separate and bear rows of claws. Procercus and two pairs of anal tubules present (Wiederholm, 1983; Moller Pillot, 1984b).
Head
The headcapsule is dark brown.
Antenna
The antenna consists of five segments. The blade is shorter than the flagellum and the lauterborn organs are distinct Eudact fuscimanus antenna.
Mentum
The mentum has one median tooth and 6 pairs of lateral teeth. The ventromental plates are weak. The beard is absent (Wiederholm, 1983).
Labrum
The pecten epipharyngis consists of three scales, SI is bifid (Wiederholm, 1983; Moller Pillot, 1984b).
Mandible
The mandible has an apical tooth of normal length and 3 inner teeth (Wiederholm, 1983).
Differential characteristics
Orthocladius can be separated from all other genera, except Paratrichocladius, by the bifid SI, mentum with 1 median tooth and 6-9 pairs of lateral teeth, 5 segmented antenna (4 in O. consobrinus) and simpel body seta. Paratrichocladius however has a blueish thorax in freshly preserved larvae and a lobed ring beneath the ssd of the mandible. Both characters are absent in Orthocladius.
Orthocladius gr. fuscimanus can be separated from all other Orthocladius by:
dark brown head and distinct lauterborn organs on the antenna Eudact fuscimanus antenna.